Semiconductor device and method of dual-molding die formed on opposite sides of build-up interconnect structure

ABSTRACT

A semiconductor device has a first interconnect structure. A first semiconductor die has an active surface oriented towards and mounted to a first surface of the first interconnect structure. A first encapsulant is deposited over the first interconnect structure and first semiconductor die. A second semiconductor die has an active surface oriented towards and mounted to a second surface of the first interconnect structure opposite the first surface. A plurality of first conductive pillars is formed over the second surface of the first interconnect structure and around the second semiconductor die. A second encapsulant is deposited over the second semiconductor die and around the plurality of first conductive pillars. A second interconnect structure including a conductive layer and bumps are formed over the second encapsulant and electrically connect to the plurality of first conductive pillars and the first and second semiconductor die.

CLAIM TO DOMESTIC PRIORITY

The present application is a continuation of U.S. patent applicationSer. No. 13/241,153, now U.S. Pat. No. 8,264,080, filed Sep. 22, 2011,which is a division of U.S. patent application Ser. No. 12/540,174,filed Aug. 12, 2009, now U.S. Pat. No. 8,039,304, which applications areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates in general to semiconductor devices and,more particularly, to a semiconductor device and method of dual-moldingsemiconductor die mounted to opposite sides of a build-up interconnectstructure in a fan-out wafer level chip scale package.

BACKGROUND OF THE INVENTION

Semiconductor devices are commonly found in modern electronic products.Semiconductor devices vary in the number and density of electricalcomponents. Discrete semiconductor devices generally contain one type ofelectrical component, e.g., light emitting diode (LED), small signaltransistor, resistor, capacitor, inductor, and power metal oxidesemiconductor field effect transistor (MOSFET). Integrated semiconductordevices typically contain hundreds to millions of electrical components.Examples of integrated semiconductor devices include microcontrollers,microprocessors, charged-coupled devices (CCDs), solar cells, anddigital micro-mirror devices (DMDs).

Semiconductor devices perform a wide range of functions such ashigh-speed calculations, transmitting and receiving electromagneticsignals, controlling electronic devices, transforming sunlight toelectricity, and creating visual projections for television displays.Semiconductor devices are found in the fields of entertainment,communications, power conversion, networks, computers, and consumerproducts. Semiconductor devices are also found in military applications,aviation, automotive, industrial controllers, and office equipment.

Semiconductor devices exploit the electrical properties of semiconductormaterials. The atomic structure of semiconductor material allows itselectrical conductivity to be manipulated by the application of anelectric field or base current or through the process of doping. Dopingintroduces impurities into the semiconductor material to manipulate andcontrol the conductivity of the semiconductor device.

A semiconductor device contains active and passive electricalstructures. Active structures, including bipolar and field effecttransistors, control the flow of electrical current. By varying levelsof doping and application of an electric field or base current, thetransistor either promotes or restricts the flow of electrical current.Passive structures, including resistors, capacitors, and inductors,create a relationship between voltage and current necessary to perform avariety of electrical functions. The passive and active structures areelectrically connected to form circuits, which enable the semiconductordevice to perform high-speed calculations and other useful functions.

Semiconductor devices are generally manufactured using two complexmanufacturing processes, i.e., front-end manufacturing, and back-endmanufacturing, each involving potentially hundreds of steps. Front-endmanufacturing involves the formation of a plurality of die on thesurface of a semiconductor wafer. Each die is typically identical andcontains circuits formed by electrically connecting active and passivecomponents. Back-end manufacturing involves singulating individual diefrom the finished wafer and packaging the die to provide structuralsupport and environmental isolation.

One goal of semiconductor manufacturing is to produce smallersemiconductor devices. Smaller devices typically consume less power,have higher performance, and can be produced more efficiently. Inaddition, smaller semiconductor devices have a smaller footprint, whichis desirable for smaller end products. A smaller die size may beachieved by improvements in the front-end process resulting in die withsmaller, higher density active and passive components. Back-endprocesses may result in semiconductor device packages with a smallerfootprint by improvements in electrical interconnection and packagingmaterials.

The electrical interconnection in a fan-out wafer level chip scalepackage (FO-WLCSP) containing semiconductor devices stacked on multiplelevels can be accomplished with conductive through silicon vias (TSV),through hole vias (THV), or Cu-plated conductive pillars. Vias areformed in silicon or organic material around the die using laserdrilling or deep reactive ion etching (DRIE). The vias are filled withconductive material, for example by copper deposition using anelectroplating process, to form the conductive TSVs and THVs. The TSVsand THVs further connect through build-up interconnect structures whichare formed across each semiconductor die. The TSVs and THVS and build-upinterconnect structure have limited input/output (I/O) pin count andinterconnect capability, particularly for FO-WLCSP.

The semiconductor die are typically mounted to one side of the build-upinterconnect structure in the FO-WLCSP. To accommodate the die, thebuild-up interconnect structure must be relatively large, whichincreases manufacturing cost. Alternatively, if the die are mounted toboth sides of the build-up interconnect structure, the height of thebumps must be greater than the height of the upper die in order to bondthe bumps to the build-up interconnect structure. The large height andcorresponding width of the bumps increases the bump pitch and reducesI/O pin count, which is counterproductive for FO-WLCSP.

SUMMARY OF THE INVENTION

A need exists for a higher I/O pin count in FO-WLCSP. Accordingly, inone embodiment, the present invention is a method of making asemiconductor device comprising the steps of providing a firstsemiconductor component, depositing a first encapsulant over the firstsemiconductor component, forming a first interconnect structure over thefirst semiconductor component, mounting a second semiconductor componentto the first interconnect structure, depositing a second encapsulantover the second semiconductor component and first interconnectstructure, and forming a second interconnect structure over the secondencapsulant

In another embodiment, the present invention is a method of making asemiconductor device comprising the steps of providing a firstsemiconductor component, depositing a first encapsulant over the firstsemiconductor component, forming a first interconnect structure over thefirst semiconductor component, mounting a second semiconductor componentto the first interconnect structure, and depositing a second encapsulantover the second semiconductor component.

In another embodiment, the present invention is a method of making asemiconductor device comprising the steps of providing a firstsemiconductor component, depositing a first encapsulant over the firstsemiconductor component, forming a first interconnect structure over thefirst semiconductor component, and mounting a second semiconductorcomponent to the first interconnect structure.

In another embodiment, the present invention is a semiconductor devicecomprising a first semiconductor component and first encapsulantdeposited over the first semiconductor component. A first interconnectstructure is formed over the first semiconductor component. A secondsemiconductor component is mounted to the first interconnect structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a PCB with different types of packages mounted to itssurface;

FIGS. 2 a-2 c illustrate further detail of the representativesemiconductor packages mounted to the PCB;

FIGS. 3 a-3 h illustrate a process of dual-molding semiconductor diemounted to opposite sides of build-up interconnect structure in aFO-WLCSP;

FIG. 4 illustrates the WLCSP with dual-molded semiconductor die mountedto opposite sides of build-up interconnect structure;

FIG. 5 illustrates the dual-molded die with conductive pillars extendingfrom the encapsulant;

FIG. 6 illustrates the dual-molded die with the conductive pillarsrecessed with respect to the encapsulant;

FIG. 7 illustrates the dual-molded die with an exposed backside of thelower and upper semiconductor die;

FIG. 8 illustrates a build-up interconnect structure formed over uppersemiconductor die;

FIG. 9 illustrates an EMI shielding layer formed over uppersemiconductor die; and

FIG. 10 illustrates discrete semiconductor components mounted tobuild-up interconnect structure.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention is described in one or more embodiments in thefollowing description with reference to the figures, in which likenumerals represent the same or similar elements. While the invention isdescribed in terms of the best mode for achieving the invention'sobjectives, it will be appreciated by those skilled in the art that itis intended to cover alternatives, modifications, and equivalents as maybe included within the spirit and scope of the invention as defined bythe appended claims and their equivalents as supported by the followingdisclosure and drawings.

Semiconductor devices are generally manufactured using two complexmanufacturing processes: front-end manufacturing and back-endmanufacturing. Front-end manufacturing involves the formation of aplurality of die on the surface of a semiconductor wafer. Each die onthe wafer contains active and passive electrical components, which areelectrically connected to form functional electrical circuits. Activeelectrical components, such as transistors and diodes, have the abilityto control the flow of electrical current. Passive electricalcomponents, such as capacitors, inductors, resistors, and transformers,create a relationship between voltage and current necessary to performelectrical circuit functions.

Passive and active components are formed over the surface of thesemiconductor wafer by a series of process steps including doping,deposition, photolithography, etching, and planarization. Dopingintroduces impurities into the semiconductor material by techniques suchas ion implantation or thermal diffusion. The doping process modifiesthe electrical conductivity of semiconductor material in active devices,transforming the semiconductor material into an insulator, conductor, ordynamically changing the semiconductor material conductivity in responseto an electric field or base current. Transistors contain regions ofvarying types and degrees of doping arranged as necessary to enable thetransistor to promote or restrict the flow of electrical current uponthe application of the electric field or base current.

Active and passive components are formed by layers of materials withdifferent electrical properties. The layers can be formed by a varietyof deposition techniques determined in part by the type of materialbeing deposited. For example, thin film deposition may involve chemicalvapor deposition (CVD), physical vapor deposition (PVD), electrolyticplating, and electroless plating processes. Each layer is generallypatterned to form portions of active components, passive components, orelectrical connections between components.

The layers can be patterned using photolithography, which involves thedeposition of light sensitive material, e.g., photoresist, over thelayer to be patterned. A pattern is transferred from a photomask to thephotoresist using light. The portion of the photoresist patternsubjected to light is removed using a solvent, exposing portions of theunderlying layer to be patterned. The remainder of the photoresist isremoved, leaving behind a patterned layer. Alternatively, some types ofmaterials are patterned by directly depositing the material into theareas or voids formed by a previous deposition/etch process usingtechniques such as electroless and electrolytic plating.

Depositing a thin film of material over an existing pattern canexaggerate the underlying pattern and create a non-uniformly flatsurface. A uniformly flat surface is required to produce smaller andmore densely packed active and passive components. Planarization can beused to remove material from the surface of the wafer and produce auniformly flat surface. Planarization involves polishing the surface ofthe wafer with a polishing pad. An abrasive material and corrosivechemical are added to the surface of the wafer during polishing. Thecombined mechanical action of the abrasive and corrosive action of thechemical removes any irregular topography, resulting in a uniformly flatsurface.

Back-end manufacturing refers to cutting or singulating the finishedwafer into the individual die and then packaging the die for structuralsupport and environmental isolation. To singulate the die, the wafer isscored and broken along non-functional regions of the wafer called sawstreets or scribes. The wafer is singulated using a laser cutting toolor saw blade. After singulation, the individual die are mounted to apackage substrate that includes pins or contact pads for interconnectionwith other system components. Contact pads formed over the semiconductordie are then connected to contact pads within the package. Theelectrical connections can be made with solder bumps, stud bumps,conductive paste, or wirebonds. An encapsulant or other molding materialis deposited over the package to provide physical support and electricalisolation. The finished package is then inserted into an electricalsystem and the functionality of the semiconductor device is madeavailable to the other system components.

FIG. 1 illustrates electronic device 50 having a chip carrier substrateor printed circuit board (PCB) 52 with a plurality of semiconductorpackages mounted on its surface. Electronic device 50 may have one typeof semiconductor package, or multiple types of semiconductor packages,depending on the application. The different types of semiconductorpackages are shown in FIG. 1 for purposes of illustration.

Electronic device 50 may be a stand-alone system that uses thesemiconductor packages to perform one or more electrical functions.Alternatively, electronic device 50 may be a subcomponent of a largersystem. For example, electronic device 50 may be a graphics card,network interface card, or other signal processing card that can beinserted into a computer. The semiconductor package can includemicroprocessors, memories, application specific integrated circuits(ASIC), logic circuits, analog circuits, RF circuits, discrete devices,or other semiconductor die or electrical components.

In FIG. 1, PCB 52 provides a general substrate for structural supportand electrical interconnect of the semiconductor packages mounted on thePCB. Conductive signal traces 54 are formed over a surface or withinlayers of PCB 52 using evaporation, electrolytic plating, electrolessplating, screen printing, or other suitable metal deposition process.Signal traces 54 provide for electrical communication between each ofthe semiconductor packages, mounted components, and other externalsystem components. Traces 54 also provide power and ground connectionsto each of the semiconductor packages.

In some embodiments, a semiconductor device has two packaging levels.First level packaging is a technique for mechanically and electricallyattaching the semiconductor die to an intermediate carrier. Second levelpackaging involves mechanically and electrically attaching theintermediate carrier to the PCB. In other embodiments, a semiconductordevice may only have the first level packaging where the die ismechanically and electrically mounted directly to the PCB.

For the purpose of illustration, several types of first level packaging,including wire bond package 56 and flip chip 58, are shown on PCB 52.Additionally, several types of second level packaging, including ballgrid array (BGA) 60, bump chip carrier (BCC) 62, dual in-line package(DIP) 64, land grid array (LGA) 66, multi-chip module (MCM) 68, quadflat non-leaded package (QFN) 70, and quad flat package 72, are shownmounted on PCB 52. Depending upon the system requirements, anycombination of semiconductor packages, configured with any combinationof first and second level packaging styles, as well as other electroniccomponents, can be connected to PCB 52. In some embodiments, electronicdevice 50 includes a single attached semiconductor package, while otherembodiments call for multiple interconnected packages. By combining oneor more semiconductor packages over a single substrate, manufacturerscan incorporate pre-made components into electronic devices and systems.Because the semiconductor packages include sophisticated functionality,electronic devices can be manufactured using cheaper components and astreamlined manufacturing process. The resulting devices are less likelyto fail and less expensive to manufacture resulting in a lower cost forconsumers.

FIGS. 2 a-2 c show exemplary semiconductor packages. FIG. 2 aillustrates further detail of DIP 64 mounted on PCB 52. Semiconductordie 74 includes an active region containing analog or digital circuitsimplemented as active devices, passive devices, conductive layers, anddielectric layers formed within the die and are electricallyinterconnected according to the electrical design of the die. Forexample, the circuit may include one or more transistors, diodes,inductors, capacitors, resistors, and other circuit elements formedwithin the active region of semiconductor die 74. Contact pads 76 areone or more layers of conductive material, such as aluminum (Al), copper(Cu), tin (Sn), nickel (Ni), gold (Au), or silver (Ag), and areelectrically connected to the circuit elements formed withinsemiconductor die 74. During assembly of DIP 64, semiconductor die 74 ismounted to an intermediate carrier 78 using a gold-silicon eutecticlayer or adhesive material such as thermal epoxy. The package bodyincludes an insulative packaging material such as polymer or ceramic.Conductor leads 80 and wire bonds 82 provide electrical interconnectbetween semiconductor die 74 and PCB 52. Encapsulant 84 is depositedover the package for environmental protection by preventing moisture andparticles from entering the package and contaminating die 74 or wirebonds 82.

FIG. 2 b illustrates further detail of BCC 62 mounted on PCB 52.Semiconductor die 88 is mounted over carrier 90 using an underfill orepoxy-resin adhesive material 92. Wire bonds 94 provide first levelpacking interconnect between contact pads 96 and 98. Molding compound orencapsulant 100 is deposited over semiconductor die 88 and wire bonds 94to provide physical support and electrical isolation for the device.Contact pads 102 are formed over a surface of PCB 52 using a suitablemetal deposition process such as electrolytic plating or electrolessplating to prevent oxidation. Contact pads 102 are electricallyconnected to one or more conductive signal traces 54 in PCB 52. Bumps104 are formed between contact pads 98 of BCC 62 and contact pads 102 ofPCB 52.

In FIG. 2 c, semiconductor die 58 is mounted face down to intermediatecarrier 106 with a flip chip style first level packaging. Active region108 of semiconductor die 58 contains analog or digital circuitsimplemented as active devices, passive devices, conductive layers, anddielectric layers formed according to the electrical design of the die.For example, the circuit may include one or more transistors, diodes,inductors, capacitors, resistors, and other circuit elements withinactive region 108. Semiconductor die 58 is electrically and mechanicallyconnected to carrier 106 through bumps 110.

BGA 60 is electrically and mechanically connected to PCB 52 with a BGAstyle second level packaging using bumps 112. Semiconductor die 58 iselectrically connected to conductive signal traces 54 in PCB 52 throughbumps 110, signal lines 114, and bumps 112. A molding compound orencapsulant 116 is deposited over semiconductor die 58 and carrier 106to provide physical support and electrical isolation for the device. Theflip chip semiconductor device provides a short electrical conductionpath from the active devices on semiconductor die 58 to conductiontracks on PCB 52 in order to reduce signal propagation distance, lowercapacitance, and improve overall circuit performance. In anotherembodiment, the semiconductor die 58 can be mechanically andelectrically connected directly to PCB 52 using flip chip style firstlevel packaging without intermediate carrier 106.

FIGS. 3 a-3 h illustrate, in relation to FIGS. 1 and 2 a-2 c, a processof dual-molding semiconductor die mounted to opposite sides of abuild-up interconnect structure in a FO-WLCSP. In FIG. 3 a, a wafer-formsubstrate or carrier 120 contains temporary or sacrificial base materialsuch as silicon, polymer, polymer composite, metal, ceramic, glass,glass epoxy, beryllium oxide, or other suitable low-cost, rigid materialor bulk semiconductor material for structural support. Carrier 120 canbe tape. An optional interface layer 122 can be formed over carrier 120as a temporary bonding film or etch-stop layer.

In FIG. 3 b, semiconductor die or components 124 are mounted tointerface layer 122 with contact pads 126 on active surface 128 orientedtoward carrier 120. Active surface 128 contains analog or digitalcircuits implemented as active devices, passive devices, conductivelayers, and dielectric layers formed within the die and electricallyinterconnected according to the electrical design and function of thedie. For example, the circuit may include one or more transistors,diodes, and other circuit elements formed within active surface 128 toimplement analog circuits or digital circuits, such as digital signalprocessor (DSP), ASIC, memory, or other signal processing circuit.Semiconductor die 124 may also contain IPD, such as inductors,capacitors, and resistors, for RF signal processing. A typical RF systemrequires multiple IPDs in one or more semiconductor packages to performthe necessary electrical functions.

In FIG. 3 c, an encapsulant or molding compound 130 is deposited overcarrier 120 and active surface 128 of semiconductor die 124 using apaste printing, compressive molding, transfer molding, liquidencapsulant molding, vacuum lamination, spin coating, or other suitableapplicator. Encapsulant 130 can be polymer composite material, such asepoxy resin with filler, epoxy acrylate with filler, or polymer withproper filler. Encapsulant 130 is non-conductive and environmentallyprotects the semiconductor device from external elements andcontaminants.

The intermediate structure described in FIGS. 3 a-3 c is inverted andcarrier 120 and optional interface layer 122 are removed by chemicaletching, mechanical peel-off, CMP, mechanical grinding, thermal bake,laser scanning, or wet stripping, as shown in FIG. 3 d. A build-upinterconnect structure 132 is formed over semiconductor die 124 and asurface of encapsulant 130. The build-up interconnect structure 132includes an insulating or passivation layer 134 containing one or morelayers of silicon dioxide (SiO2), silicon nitride (Si3N4), siliconoxynitride (SiON), tantalum pentoxide (Ta2O5), aluminum oxide (Al2O3),or other material having similar insulating and structural properties.The insulating layer 134 is formed using PVD, CVD, printing, spincoating, spray coating, sintering or thermal oxidation.

The build-up interconnect structure 132 further includes an electricallyconductive layer 136 formed in insulating layer 134 using a patterningand deposition process such as PVD, CVD, sputtering, electrolyticplating, and electroless plating process. Conductive layer 136 can beone or more layers of Al, Cu, Sn, Ni, Au, Ag, or other suitableelectrically conductive material. One portion of conductive layer 136 iselectrically connected to contact pads 126 of semiconductor die 124.Other portions of conductive layer 136 can be electrically common orelectrically isolated depending on the design and function of thesemiconductor device.

In FIG. 3 e, one or more layers of photoresist are deposited over asurface of build-up interconnect structure 132 opposite semiconductordie 124. A portion of the photoresist is exposed and removed by an etchdevelopment process to form vias. Conductive material, such as Al, Cu,Sn, Ni, Au, Ag, titanium (Ti), tungsten (W), solder, poly-silicon, orcombination thereof, is deposited in the vias using a selective platingprocess. The photoresist is stripped away leaving behind individualconductive pillars 140. In another embodiment, conductive pillars 140can be formed as stud bumps or stacked bumps.

In FIG. 3 f, semiconductor die or components 142 are mounted betweenconductive pillars 140 with contact pads 144 on active surface 146oriented to the surface of build-up interconnect structure 132 oppositesemiconductor die 124. Contact pads 144 are electrically connected toconductive layer 136 with bumps 147. Active surface 146 contains analogor digital circuits implemented as active devices, passive devices,conductive layers, and dielectric layers formed within the die andelectrically interconnected according to the electrical design andfunction of the die. For example, the circuit may include one or moretransistors, diodes, and other circuit elements formed within activesurface 146 to implement analog circuits or digital circuits, such asDSP, ASIC, memory, or other signal processing circuit. Semiconductor die142 may also contain IPD, such as inductors, capacitors, and resistors,for RF signal processing.

In FIG. 3 g, an encapsulant or molding compound 148 is deposited overbuild-up interconnect structure 132 and semiconductor die 142 and aroundconductive pillars 140 using a paste printing, compressive molding,transfer molding, liquid encapsulant molding, vacuum lamination, spincoating, or other suitable applicator. Encapsulant 148 can be polymercomposite material, such as epoxy resin with filler, epoxy acrylate withfiller, or polymer with proper filler. Encapsulant 148 is non-conductiveand environmentally protects the semiconductor device from externalelements and contaminants. Encapsulant 148 is planarized by an etchingprocess to expose conductive pillars 140.

In another embodiment, semiconductor die or components 142 are mountedwith contact pads 144 on active surface 146 oriented to the surface ofbuild-up interconnect structure 132 opposite semiconductor die 124(without forming conductive pillars 140). Encapsulant 148 is depositedover build-up interconnect structure 132 and semiconductor die 142. Aplurality of vias is formed in encapsulant 148 using laser drilling oretching process, such as DRIE. The vias are filled with Al, Cu, Sn, Ni,Au, Ag, titanium (Ti), W, poly-silicon, or other suitable electricallyconductive material using PVD, CVD, electrolytic plating, electrolessplating process, or other suitable metal deposition process to formconductive vias through encapsulant 148. The conductive vias areelectrically connected to contact pads 144.

In FIG. 3 h, an interconnect structure 149 is formed over encapsulant148 and conductive pillars 140. An electrically conductive layer 150 isformed using a patterning and deposition process such as PVD, CVD,sputtering, electrolytic plating, and electroless plating process.Conductive layer 150 can be one or more layers of Al, Cu, Sn, Ni, Au,Ag, or other suitable electrically conductive material. Conductive layer150 operates as an under bump metallization layer (UBM) andredistribution layer (RDL) for a greater input/output (I/O) pin count.

An electrically conductive bump material is deposited over conductivelayer 150 and electrically connected to conductive pillars 140 using anevaporation, electrolytic plating, electroless plating, ball drop, orscreen printing process. The bump material can be Al, Sn, Ni, Au, Ag,Pb, Bi, Cu, solder, and combinations thereof, with an optional fluxsolution. For example, the bump material can be eutectic Sn/Pb,high-lead solder, or lead-free solder. The bump material is bonded toconductive layer 150 using a suitable attachment or bonding process. Inone embodiment, the bump material is reflowed by heating the materialabove its melting point to form spherical balls or bumps 152. In someapplications, bumps 152 are reflowed a second time to improve electricalcontact to conductive layer 150. The bumps can also be compressionbonded to conductive layer 150. Bumps 152 represent one type ofinterconnect structure that can be formed over conductive layer 150. Theinterconnect structure can also use bond wires, stud bump, micro bump,or other electrical interconnect.

Semiconductor die 124 are singulated with saw blade or laser cuttingdevice 154 into individual FO-WLCSP. FIG. 4 shows FO-WLCSP 160 aftersingulation. Semiconductor die 124 and 142 are mounted to opposite sidesof and electrically interconnected through build-up interconnectstructure 132. By mounting semiconductor die 124 and 142 to oppositesides of build-up interconnect structure 132, a greater utilization ofthe build-up interconnect structure can be achieved and its size can bereduced, which saves manufacturing cost. Encapsulant 130 and 148 aredeposited around semiconductor die 124 and 142, respectively. Build-upinterconnect structure 132 is electrically connected to RDL 150 andbumps 152 by z-direction interconnect conductive pillars 140, which arealso covered by encapsulant 148. By dual molding of semiconductor die124 and 142 and using conductive pillars 140 for z-directioninterconnect and RDL 150 for lateral interconnect, the pitch of bumps152 is reduced which increases the I/O pin count.

FIG. 5 shows FO-WLCSP 162 with conductive pillars 140 extending fromencapsulant 148. In this embodiment, encapsulant 148 in FIG. 3 g isetched back so that conductive pillars 140 protrude from the encapsulantfor direct interconnect to other packages or devices.

FIG. 6 shows FO-WLCSP 164 with a reduced height for conductive pillars140. In this embodiment, conductive pillars 140 and a portion ofencapsulant 148 away from semiconductor die 142 in FIG. 3 g are etchedback with respect to a portion of encapsulant 148 over semiconductor die142 to reduce the overall height of the FO-WLCSP.

FIG. 7 shows FO-WLCSP 166 with conductive pillars 140 and encapsulant148 planarized to expose a back surface of semiconductor die 142.Likewise, encapsulant 130 is planarized to expose a back surface ofsemiconductor die 124.

FIG. 8 shows FO-WLCSP 168 with conductive pillars 170 formed aroundsemiconductor die 124 and build-up interconnect layer 172 formed over asurface of encapsulant 130. In this embodiment, one or more layers ofphotoresist are deposited over carrier 120 prior to depositingencapsulant 130 in FIG. 3 c. A portion of the photoresist is exposed andremoved by an etch development process to form vias. Conductivematerial, such as Al, Cu, Sn, Ni, Au, Ag, Ti, W, solder, poly-silicon,or combination thereof, is deposited in the vias using a selectiveplating process. The photoresist is stripped away leaving behindindividual conductive pillars 170. In another embodiment, conductivepillars 170 can be formed as stud bumps or stacked bumps. The remainderof the structure is formed according to FIGS. 3 c-3 g.

A build-up interconnect structure 172 is formed over encapsulant 130 andconductive pillars 170. The build-up interconnect structure 172 includesan insulating or passivation layer 174 containing one or more layers ofSiO2, Si3N4, SiON, Ta2O5, Al2O3, or other material having similarinsulating and structural properties. The insulating layer 174 is formedusing PVD, CVD, printing, spin coating, spray coating, sintering orthermal oxidation.

The build-up interconnect structure 172 further includes an electricallyconductive layer 176 formed in insulating layer 174 using a patterningand deposition process such as PVD, CVD, sputtering, electrolyticplating, and electroless plating process. Conductive layer 176 can beone or more layers of Al, Cu, Sn, Ni, Au, Ag, or other suitableelectrically conductive material. One portion of conductive layer 176 iselectrically connected to conductive pillars 170. Other portions ofconductive layer 176 can be electrically common or electrically isolateddepending on the design and function of the semiconductor device.

In FIG. 9, FO-WLCSP 180 has shielding layer 182 formed oversemiconductor die 124 and shielding layer 184 formed over semiconductordie 142. A portion of encapsulant 130 is removed for shielding layer182, and a portion of encapsulant 148 is removed for shielding layer184. Shielding layers 182 and 184 can be Cu, Al, ferrite or carbonyliron, stainless steel, nickel silver, low-carbon steel, silicon-ironsteel, foil, epoxy, conductive resin, and other metals and compositescapable of blocking or absorbing electromagnetic interference (EMI),radio frequency interference (RFI), and other inter-device interference.Shielding layers 182 and 184 can also be a non-metal material such ascarbon-black or aluminum flake to reduce the effects of EMI and RFI.

In FIG. 10, semiconductor die or components 190 are mounted to atemporary carrier with contact pads 192 on active surface 194 orientedtoward the carrier. Active surface 194 contains analog or digitalcircuits implemented as active devices, passive devices, conductivelayers, and dielectric layers formed within the die and electricallyinterconnected according to the electrical design and function of thedie. For example, the circuit may include one or more transistors,diodes, and other circuit elements formed within active surface 194 toimplement analog circuits or digital circuits, such as DSP, ASIC,memory, or other signal processing circuit. Semiconductor die 190 mayalso contain IPD, such as inductors, capacitors, and resistors, for RFsignal processing. A typical RF system requires multiple IPDs in one ormore semiconductor packages to perform the necessary electricalfunctions.

An encapsulant or molding compound 196 is deposited over the carrier andsemiconductor die 190 using a paste printing, compressive molding,transfer molding, liquid encapsulant molding, vacuum lamination, spincoating, or other suitable applicator. Encapsulant 196 can be polymercomposite material, such as epoxy resin with filler, epoxy acrylate withfiller, or polymer with proper filler. Encapsulant 196 is non-conductiveand environmentally protects the semiconductor device from externalelements and contaminants.

The intermediate structure is inverted and the temporary carrier isremoved by chemical etching, mechanical peel-off, CMP, mechanicalgrinding, thermal bake, laser scanning, or wet stripping. A build-upinterconnect structure 198 is formed over semiconductor die 190 andencapsulant 196. The build-up interconnect structure 198 includes aninsulating or passivation layer 200 containing one or more layers ofSiO2, Si3N4, SiON, Ta2O5, Al2O3, or other material having similarinsulating and structural properties. The insulating layer 200 is formedusing PVD, CVD, printing, spin coating, spray coating, sintering orthermal oxidation.

The build-up interconnect structure 198 further includes an electricallyconductive layer 202 formed in insulating layer 200 using a patterningand deposition process such as PVD, CVD, sputtering, electrolyticplating, and electroless plating process. Conductive layer 202 can beone or more layers of Al, Cu, Sn, Ni, Au, Ag, or other suitableelectrically conductive material. One portion of conductive layer 202 iselectrically connected to contact pads 192 of semiconductor die 190.Other portions of conductive layer 202 can be electrically common orelectrically isolated depending on the design and function of thesemiconductor device.

One or more layers of photoresist are deposited over a surface ofbuild-up interconnect structure 198 opposite semiconductor die 190. Aportion of the photoresist is exposed and removed by an etch developmentprocess to form vias. Conductive material, such as Al, Cu, Sn, Ni, Au,Ag, Ti, W, solder, poly-silicon, or combination thereof, is deposited inthe vias using a selective plating process. The photoresist is strippedaway leaving behind individual conductive pillars 204. In anotherembodiment, conductive pillars 204 can be formed as stud bumps orstacked bumps.

A plurality of discrete semiconductor components 208 is mounted betweenconductive pillars 204 to the surface of build-up interconnect structure198 opposite semiconductor die 190. Discrete semiconductor components208 can be resistors, capacitors, inductors, or discrete active devices.

An encapsulant or molding compound 210 is deposited over build-upinterconnect structure 198 and discrete semiconductor components 208using a paste printing, compressive molding, transfer molding, liquidencapsulant molding, vacuum lamination, spin coating, or other suitableapplicator. Encapsulant 210 can be polymer composite material, such asepoxy resin with filler, epoxy acrylate with filler, or polymer withproper filler. Encapsulant 210 is non-conductive and environmentallyprotects the semiconductor device from external elements andcontaminants.

An interconnect structure 206 is formed over encapsulant 210. Anelectrically conductive layer 212 is formed using a patterning and metaldeposition process such as PVD, CVD, sputtering, electrolytic plating,and electroless plating. Conductive layer 212 can be one or more layersof Al, Cu, Sn, Ni, Au, Ag, or other suitable electrically conductivematerial. Conductive layer 212 operates as UBM and RDL for a greater I/Opin count.

An electrically conductive bump material is deposited over conductivelayer 212 and electrically connected to conductive pillars 204 using anevaporation, electrolytic plating, electroless plating, ball drop, orscreen printing process. The bump material can be Al, Sn, Ni, Au, Ag,Pb, Bi, Cu, solder, and combinations thereof, with an optional fluxsolution. For example, the bump material can be eutectic Sn/Pb,high-lead solder, or lead-free solder. The bump material is bonded toconductive layer 212 using a suitable attachment or bonding process. Inone embodiment, the bump material is reflowed by heating the materialabove its melting point to form spherical balls or bumps 214. In someapplications, bumps 214 are reflowed a second time to improve electricalcontact to conductive layer 212. The bumps can also be compressionbonded to conductive layer 212. Bumps 214 represent one type ofinterconnect structure that can be formed over conductive layer 212. Theinterconnect structure can also use bond wires, stud bump, micro bump,or other electrical interconnect.

While one or more embodiments of the present invention have beenillustrated in detail, the skilled artisan will appreciate thatmodifications and adaptations to those embodiments may be made withoutdeparting from the scope of the present invention as set forth in thefollowing claims.

What is claimed:
 1. A method of making a semiconductor device,comprising: providing a first semiconductor component; depositing afirst encapsulant over the first semiconductor component; forming afirst interconnect structure over the first semiconductor component;mounting a second semiconductor component to the first interconnectstructure; depositing a second encapsulant over the second semiconductorcomponent and first interconnect structure; and forming a secondinterconnect structure over the second encapsulant.
 2. The method ofclaim 1, further including forming a plurality of conductive viasthrough the first encapsulant or second encapsulant.
 3. The method ofclaim 2, wherein the conductive vias extend from the first encapsulantor second encapsulant.
 4. The method of claim 2, wherein the conductivevias are recessed with respect to a surface of the first encapsulant ora surface of the second encapsulant.
 5. The method of claim 1, furtherincluding planarizing the first encapsulant or second encapsulant. 6.The method of claim 1, wherein the first semiconductor component orsecond semiconductor component is a discrete semiconductor component. 7.A method of making a semiconductor device, comprising: providing a firstsemiconductor component; depositing a first encapsulant over the firstsemiconductor component; forming a first interconnect structure over thefirst semiconductor component; mounting a second semiconductor componentto the first interconnect structure; and depositing a second encapsulantover the second semiconductor component.
 8. The method of claim 7,further including forming a second interconnect structure over thesecond encapsulant.
 9. The method of claim 7, further including forminga second interconnect structure over the first encapsulant opposite thefirst interconnect structure.
 10. The method of claim 7, furtherincluding forming a conductive via through the first encapsulant orsecond encapsulant.
 11. The method of claim 10, wherein the conductivevia extends from the first encapsulant or second encapsulant.
 12. Themethod of claim 10, wherein the conductive via is recessed with respectto a surface of the first encapsulant or a surface of the secondencapsulant.
 13. The method of claim 7, further including forming ashielding layer over the first encapsulant or second semiconductorcomponent.
 14. A method of making a semiconductor device, comprising:providing a first semiconductor component; depositing a firstencapsulant over the first semiconductor component; forming a firstinterconnect structure over the first semiconductor component; andmounting a second semiconductor component to the first interconnectstructure.
 15. The method of claim 14, further including depositing asecond encapsulant over the second semiconductor component.
 16. Themethod of claim 15, further including forming a second interconnectstructure over the second encapsulant.
 17. The method of claim 16,further including forming a second interconnect structure over the firstencapsulant opposite the first interconnect structure.
 18. The method ofclaim 15, further including planarizing the first encapsulant or secondencapsulant.
 19. The method of claim 15, further including forming aconductive via through the first encapsulant or second encapsulant. 20.The method of claim 14, further including forming a shielding layer overthe first encapsulant or second semiconductor component.
 21. Asemiconductor device, comprising: a first semiconductor component; afirst encapsulant deposited over the first semiconductor component; afirst interconnect structure formed over the first semiconductorcomponent; and a second semiconductor component mounted to the firstinterconnect structure.
 22. The semiconductor device of claim 21,further including a second encapsulant deposited over the secondsemiconductor component.
 23. The semiconductor device of claim 22,further including a second interconnect structure formed over the secondencapsulant or the first encapsulant opposite the first interconnectstructure.
 24. The semiconductor device of claim 22, further including aconductive via formed through the first encapsulant or secondencapsulant.
 25. The semiconductor device of claim 21, further includinga shielding layer formed over the first encapsulant or secondsemiconductor component.